Conventionally, in the electric system of automobiles or the like, multiple routed electric wires are laid through and held within a wire housing protector and secured at suitable locations in order to protect the electric wires from external members that might otherwise interfere with the electric wires and restrict the routing of the electric wires.
Incidentally, as described in JP H06-70415U (Patent Document 1) for example, such a wire housing protector is constituted by a trough-shaped protector body and a lid that covers the upper opening of the protector body. Once multiple electric wires are laid through the protector body, the lid is fixed to the protector body by a locking mechanism that protrudes from a sidewall of the protector body. In this way, the protector is capable of fixedly holding the multiple electric wires accommodated therein.
Specifically, an elastic projecting piece is provided at an outer peripheral edge of the lid and protrudes toward the protector body, and an elastic projecting piece insertion portion having a frame shape is provided in a side wall of the protector body. A claw-shaped engagement protrusion is provided on an outer surface of its leading end of the elastic projecting piece, and when the elastic projecting piece is inserted into the elastic projecting piece insertion portion, the engagement protrusion is brought into contact with a side surface of the elastic projecting piece insertion portion, and the leading end of the elastic projecting piece is elastically deformed and is pressed toward an inner surface side. Accordingly, the elastic projecting piece is allowed to be inserted into the elastic projecting piece insertion portion. Furthermore, when the elastic projecting piece is inserted up to an insertion end position, contact of the engagement protrusion to the side surface of the elastic projecting piece insertion portion is released, and the elastic projecting piece undergoes elastic restoration. Accordingly, the engagement protrusion is arranged directly under the engagement portion that is provided in a lower portion of the elastic projecting piece insertion portion, and the engagement protrusion can engage with the engagement portion. When a force is applied to the lid in a direction such that the lid separates from the protector body, the engagement protrusion engages with the engagement portion, and as a result, the separation of the lid is inhibited and the lid is held by the protector body.
However, in such a locking mechanism having a conventional structure, when a very strong upward force is applied to the lid in a direction separating it from the protector body, the engagement protrusion is pulled while inclining obliquely upward as the elastic projecting piece moves upward, and there is a risk that the lid separates from the engagement portion.
Therefore, the applicant proposed, in JP 2014-183690A (Patent Document 2), a structure in which a protrusion that rises vertically upward from a projection leading end of the engagement protrusion is provided, and the separation of the engagement protrusion from the engagement portion is inhibited as a result of causing the protrusion to engage with an outer surface of the elastic projecting piece insertion portion. However, with the increasing demand for higher component density and space saving in vehicles in recent years, further improvement of the locking mechanism that can exert a strong retaining force without increasing the size has been demanded.